Gently fold beaten egg whites into lemon mixture. Divide batter among the prepared ramekins. Place the ramekins in a roasting pan. Transfer to the oven and carefully add enough hot water to come halfway up the sides of the ramekins.

Bake until set around the edges but still jiggly in the center, and until tops are lightly browned, 35 to 40 minutes. Transfer the ramekins to a wire rack.